Protective device

ABSTRACT

133,187. British Thomson - Houston Co., and Wedmore, E. B. Oct. 17, 1918. Protective arrangements.-In an arrangement of the Merz-Price type, lack of balance between the balancing-transformers at the ends of feeders &amp;c. is compensated for by providing on the relays or tripping-devices of the system additional coils excited by the current of the system (and producing forces proportional to the current of the system) tending to restrain the relays from operating. In the arangement shown in Fig. 1, the operating- windings 2 of the relays are connected in the pilot-wire system in series with the restraining windings 1, which are connected across the transformers 4. The relays are normally held in the operative position by the restraining-coils and may have a mechanical bias in the same direction. The effect of capacity currents in the pilot wires may be annuled to some degree by a condenser inserted across the transformers in series with the restraining-windings. Capacity currents may, however, be dealt with by a compensating-winding 7, Fig. 3, connected in series with a condenser 8 and in parallel with the restraining coil, as described in Specification 17177/10, to produce a magneto-motive force opposing that produced by the current in the operating winding. The restraining-windings may be connected, in series with the condenser and compensating-winding, across the transformer.

OFFICE.

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PRQTECTIVE DEVICE.

l To all whom if may concern:

'Be itknownt'hat I', EDMUND B. Wnnironn,

subject of the King of Great Bri-tain, re-

fsiding atl-london, England, have invented certain new and useful vI,mproveinents in "Protective Devices, of which the following yio is a specification.

l My invention relates to protective devices for 'electric feeders particularly to protective systems of the piloty Wire type and has for its object Ito overcome the diliiculties' eX- Vperienced in applying such protective sys- `Atems to feeders or plants of large magnitude owing-to the necessity of accurately balancing the protecting transformers and of deallng Withv the capacityl current in the pilot Wires connecting the. transformers.

It has hitherto'been'proposed in such sys? tems to overcome the effect of the capacity currentin thepilot Wire circuit by applying a compensating lelectromotive force to the circuitffbr l a .i compensating magnetomotive forcietogthe'ftrip coils or relay coils of the trippii'lg circuit of the circuitibreakers. lt has fur-therbeen proposed to overcome the ,capacity of. the` pilotl Wire circuit by means l. ,flanauiiiliary compensating conductor .or

"inasmuch as they do not compensate for the i lack of balance `which may exist between the protective'transformers when large currents How in the system. According to my inventionjlprovide on the relays or trip-coils of the-protective system restraining` or biasing coils excited by current dependent upon the feeder current. The current may he supplied frorn the current transformers of the protective system, and the biasing or restraining coils may be used alone, in combination -With. ordinary relays'or they may be used in combination With. the compensating coils hereinbefore referred to. lhey may also be fitted to the relays used with the shielded or compensated pilot Wire circuit abcve mentioned and the said relays may also be fitted with coinpensatingcoils. Figures il, 2, 3 and l of the accompanying drawings diagrammatically illustrate a protective system embodying various forms of myfinvention, ln the application of the invention illustrated in Fig. l, I vpim/ide a cir- Specication of Letters Patent.

ria-rented May 25, 1920.

Application iled October :2st, 'lilla Serial llo. 333,612.

cuit controlling device', which, -by way of example is shown as a relay comprising an operating coil opposed in its action by a restraining coil. rliese coils be connected to opposite ends of a balanced ar1n`60 or may be connected in any other way Well known in the art to produce a resultant or differential action. The'restraining coil l is connected at each end of the feeder in parallel with a protective transformer' l and 65 in series With the operating coil 2. and pilot wire 5 of the protective system. Such a r lay embodying coils l and 2 may be ar ranged in a great many forms but it is only essential that the effect of coil 1 is to re- 70 strain the effect of coil 2. Vith such an arrangement assuming that no compensation is provided for the capacity of the pilot wire circuit, the vrestraining effect on the relay would diminish with increasing frequency, While the capacity current would increase therewith. By suitably adjusting the constants of the circuit of the restraining and operating coils of the relays, an improvenient may be obtained which in some cases may be all that may be desired, as for eX- ample, in the application of my invention to existing systems, by connecting a device 6 having a condenser action and of suitable i capacity, in series 1with the restraining coil l 85 as shown in Fig. 2. "ll/lith such an arrangement no serious loss of restraining power would result from increase of frequency.

lf a restraining coil is provided on its relay as illustrated in Fig. 3 fitted, ashas 90 hitherto been proposed, with a compensating `winding 7, in series with. a condenser 8 to overcome the effect of capacity in the pilot `Wire circuit, improved results may be. obtained vand 'the effect of the restraining 95 coil may be adjusted simply by resistance 9 in series with the latter. A condenser may also' take the place of the resistance 9.

As an alternative to the last mentioned `arr'afngement which dispenses with the sepa- 100 rate condenser 1n series with the compensating coil on the relay, the restraining and compensating coils of the relay may be connected in series With the pilot Wire circuit and with a condenser device as illustrated in Fig. il. ln this case the relay has an operating coil 2 and compensating Winding 7 both of `which normally carry capacity currents but one of which carries energy current on the occurrence of .o fault. The cau l ill.

other ,ry as an e e tion the relay is J operating hy the training winding l. thus f ting 'for normal unhalancing due zinco in 'the protective trai fectivc capacity compens-L t. cuit.

What I claim as new and desire to secure by Letters Patent of the United States, is

l. In a protective system for an electric feeder, the combination with a transformer connected at each end of said. feeder, of a pilot wire or Wires coruecting the secondaries of said transforme f in electric circuit, and control devices eachend of said feeder comprising an operating coil in series with each transformer secondary, a restraining coil in an independent circuit in shunt to nach secondary, and means having a condenser action in series with said restraining on of the pilot Wire cir- 9J. In a protective system for an electric feeder, the comhination with a transformer connected at each end of said feeder, of a pilot Wire or Wires connecting the secondaries of sail transformers in an electric circuit, and control devices at each end of said feeder comprising an operating coil in series with each transformer secondary, and means for compensating for the effect of capacity current in said pilot Wire circuit including a restraining coil in an independent shunt circuit to each secondary and device having a condenser action in series with restraining coil.

2li. In a protective system for an electric feeder, the combination with a transformer connected at each end of said feeder, of a pilot wire or y'Wires connecting the secondaries of said transformers in an electric circuit, and control devices at each end of said feeder comprising an operating coil in series with each transformer seconda; anc compensating for overcoming the capacinfinies itv effect of said pilot wire, includin a reity eliect of said pilot wire including a restraining coil in a separate circuit in shunt to each secondary and opposing the action of said operating coil, and means for changing the effect of said restraining coil including a resistance in series therewith.

5. In a protective system for an electric feeder, the combination with a transformer connected at each end of said feeder, of a pilot wire or Wires connecting the secondaries of said transformers in an electric circuit, and control devices at each end of saidfeeder comprising an operating coil, a restraining coil opposing the action of said operating coil, a compensating coil in shunt to each transformer secondary, and a condenserfin series With said compensating coil.

6. In a protective system for an electric feeder, the combination With a transformer connected at each end of said feeder, of a pilot Wire or Wires connecting the secondaries of said transformers in a series circuit and control devices at each end of said feeder comprising an operating coil, a restraining coil, and means in series With said restraining coil to compensate for the capacity effect in said pilot wire current due to change of frequency. V

In Witness whereof I have hereunto set my hand this 29 day of Sept., 1919.

EDMUND BASIL WEDMORE. 

